Method for low temperature chemical vapor deposition of low-k films using selected cyclosiloxane and ozone gases for semiconductor applications

Abstract

A method is described for forming a low-k dielectric film, in particular, a pre-metal dielectric (PMD) on a semiconductor wafer which has good gap-filling characteristics. The method uses a thermal sub-atmospheric CVD process that includes a carbon-containing organometallic precusor such as TMCTS or OMCTS, an ozone-containing gas, and a source of dopants for gettering alkali elements and for lowering the reflow temperature of the dielectric while attaining the desired low-k and gap-filling properties of the dielectric film. Phosphorous is a preferred dopant for gettering alkali elements such as sodium. Additional dopants for lowering the reflow temperature include, but are not limited to boron, germanium, arsenic, fluorine or combinations thereof.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS[0001]This Patent Application is a Divisional Patent Application of U.S. patent application Ser. No. 09 / 928,209, filed on Aug. 10, 2002.FIELD OF THE INVENTION[0002]The present invention relates to semiconductor processing, and more particularly to a process for forming a blanket dielectric layer to fill gaps between device elements.BACKGROUND OF THE INVENTION[0003]In the manufacturing of semiconductor devices, as the dimensions have shrunk, it has become more challenging to provide dielectric film layers that provide adequate electrical isolation between interconnect features and device components in order to minimize RC delay and crosstalk. One method of doing this is to provide dielectric layers using materials having lower dielectric constants (low-k dielectrics) than conventional dielectric materials such as silicon dioxide (SiO2) or silicon nitride. Low-k dielectrics typically have dielectric constants below about 4, where air has a...

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Benefits of technology

[0017]The present invention addresses the above-described need by providing a method for depositing a pre-metal low-k dielec

Problems solved by technology

In the manufacturing of semiconductor devices, as the dimensions have shrunk, it has become more challenging to provide dielectric film layers that provide adequate electrical isolation between interconnect features and device components in order to minimize RC delay and crosstalk.

However, the CVD processes, in particular PECVD, may not adequately fill the spaces or gaps between existing metal features, and may leave voids in the dielectric blanket layer which can cause problems such as micro-cracking, lack of structural support, trapping of gases or moisture or allow subsequent metal fill processes to connect nearby voids which can result in shorted device elements.

Although films provided by spin-on deposition may adequately fill spaces or gaps, these films are usually porous and would be incompatible with other MOL processing steps by being susceptible to problems such as those mentioned above.

The problem of adequate gap fill can be particularly difficult if the aspect ratio (AR), which is the ratio of height to width of the gaps, is above about 1.0.

However, PECVD solutions at the MOL level are not easily utilized, because PECVD processes may leave voids in high aspect ratio gaps, where the gap AR exceeds about 1.0.

In addition, plasma processing is not a preferred fill method for MOL as it may cause charge damage to gate oxides.

Low pressure CVD will not provide good gap filling results for chemistry such as oxygen plus an organometallic or organosilicon precursor such as TMCTS.

However, using low-k materials for AR greater than 1, SACVD may also leave voids depending on the shape of the gap to be filled.

However, because the process conditions for depositing low-k films that would also provide good gap-filling results are quite sensitive to the composition of reactant gases and the structure of the gaps to be filled, the addition of dopants which reduce the reflow temperature would not necessarily preserve the desired low-k and gap-filling properties of the film, and may require significant experimentation to achieve the desired results.

However, the increased concentration of hydroxyl radicals may lead to a porous film

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